Several games have had hacks- the word you want to be looking for is "total conversion" with the zelda hacks forming a fairly shining example and the other must have in that world is usually cited as dragoon x omega II. Several people are working on DS ones and some of the hacks for advance wars on the GBA got pretty in depth.http://www.romhacking.net/?genre=&plat...le=&author= is a start but they tend not to host a lot of the pokemon and advance wars hacks- these days such hacks are done with nice graphical tools so you get quite a few simplistic hacks and others with more merit get lost in the noise.

With that clarification though it gets kind of odd- save for the levels and assets many of the old 90s and early 2000s games got open sourced and even more were reverse engineered or remade from the ground up and it some it some fairly extensive mods and ports to all sorts of devices were made. Given a huge chunk of most handheld and "marketplace"/non expansion pack DLC is ports and remakes of older games that falls into this category....

For me though one of the nicest things about homebrew is you do not have to do things publishers like/that would result in games sales or indeed have to follow modern trends (the homebrew world would be thrilled to have an old school adventure game but you probably would not make it past the front door of most publishers today) if you instead prefer to do/try something interesting/creative- http://www.projectaon.org/staff/jens/ (PS if you are after top quality homebrew http://www.projectaon.org/staff/frederic/ ).

fast brought up the total conversion topic and this got me thinking about doom.

if you enjoy doom as a first person shooter then you should give some of the player made wads a try.

with the new build of ds doom you can load pwads without having to use any crazy tools. in the past we had to "merge" pwads with doom iwads so that ds doom would load them. now you can use the homebrew menu and the steps below...

1. grab the hb menu: http://devkitpro.org/hbmenu
2. open a basic format stripping text editor (like notepad) and type the following: dsdoom.nds -iwad doom2.wad -file name.wad -save name
..dsdoom.nds = name of the nds homebrew emu
..dsdoom2.wad = name of the doom2 official retail wad (found on the floppy or cd release)
..name.wad = the name of the pwad file
..-save name = name of the save directory
3. save this file as whatevername.argv
4. boot up your flash kit and run the homebrew menu
5. launch the argv file instead of the .nds file.

you will need a full registered version of doom1, 2, etc. make sure you load the correct version of doom for the pwad file. some are built around doom 1, some around doom 2, etc. freedoom will do the trick for most pwads and it is free, however it isn't a perfect solution. you can get freedoom here: http://www.nongnu.org/freedoom/